Simultaneous activation of multiple face representations

Humans are highly skilled at familiar face recognition, as we are able to recognize and distinguish between thousands of individual facial identities. Given this remarkable number of known faces, it seems surprising that we confuse familiar faces only very rarely. One potential explanation is that the activation of a memory representation of a particular known face results in the simultaneous inhibition of all other face representations. If correct, this would allow the activation of only a single facial representation at any given time, so preventing the brain from mixing up different facial identities. Here, we used event-related potentials to examine the neurophysiological basis of this hypothesized inhibitory process, and tested whether it is possible to have multiple face representations activated at the same time. Using individualized stimuli sets of highly familiar celebrity faces in an immediate repetition priming paradigm, we presented participants (N = 30) with prime displays consisting of (i) two images of the subsequent target facial identity (Double Repetition), (ii) two images of different facial identities, one of which showed the target identity (Single Repetition), or (iii) two images of two different facial identities (Non-Repetition), neither of which showed the following target identity. We observed clear N250r effects, consisting of more negative amplitudes at occipito-temporal channels for both the Double and Single Repetition conditions relative to the Non-Repetition condition. Moreover, Double and Single Repetition conditions were highly similar and did not significantly differ from each other. At variance with the inhibition hypothesis, this finding suggests that the brain can keep at least two different facial identities activated simultaneously.